Generally, a seat device for a vehicle includes a lifting mechanism by which a positional height of the seat cushion can be adjusted. Specifically, when an occupant sitting on the seat operates an operation lever, the lifting mechanism is operated so that the positional height of the seat cushion is adjusted. The seat device having the abovementioned configuration is disclosed, for example, in JP2002-321551A.
As illustrated in FIG. 3 of JP2002-321551A, a front link 71 and a rear link 81 are provided between an upper rail 13 and a lower arm 20. Specifically, one end portion of the front link 71 is rotatably attached to a front portion of the upper rail 13 by means of a pin 72, and the other end portion of the front link 71 is rotatably attached to a front portion of the lower arm 20 by means of a pin 73. On the other hand, one end portion of the rear link 81 is rotatably attached at to rear portion of the upper rail 13 by means of a pin 82, and the other end portion of the rear link 81 is rotatably attached to a rear portion of the lower arm 20 by means of a pin 83. In this configuration, a four-link mechanism is formed with a combination of the upper rail 13, the front link 71, the lower arm 20 and the rear link 81, each connecting as mentioned above. By virtue of the four-link mechanism, the lower arm 20 is lifted up and down relative to the upper rail 13 by rotating the front link 71 or the rear link 81.
Further, a driven gear 91 (hereinafter referred to as a sector gear 91) meshing with a pinion gear 101 is rotatably attached to a central portion of the lower arm 20 by means of a pin 92, and the rear link 81 is indirectly connected to the sector gear 91 via a connecting link 95. Furthermore, an elongated hole 91a is formed on the sector gear 91 in a manner where it extends along a partial circumference of an imaginary circle formed relative to the pin 92. In this configuration, a pin 104 is inserted into the elongated hole 91a so as to be slidable in order to limit the rotation of the sector gear 91.
According to the seat device disclosed in JP2002-321551A having the abovementioned configuration, because the sector gear 91 is simply attached to the lower arm 20 by means of the pin 92, in other words, because the sector gear 91 is cantilevered by the lower arm 20 using the pin 91, when a load is applied to the vehicle from the outside due to, for example, a vehicle collision, a buckling deformation occurs at the lower arm 20, and then force in a front-rear direction of the vehicle is applied to a meshing portion between the sector gear 91 and a pinion gear 101, as a result, the pinion gear 101 may disengage from the sector gear 91 because of the load applied to the vehicle.
A need thus exists for a seat device which is not susceptible to the drawback mentioned above.